The vicious cycle between transglutaminase 2 and reactive oxygen species in hyperglycemic memory-induced endothelial dysfunction

Endothelial versus Metabolic Insulin Resistance, A Descriptive Review

Cardiovascular complications are a primary focus in the clinical management of type 2 diabetes, as they are the leading causes of disability and mortality in individuals with diabetes. Insulin resistance and endothelial dysfunction commonly coexist in diabetic patients. An increasing body of research indicates a reciprocal and interconnected association between endothelial function and insulin resistance. Insulin resistance can manifest in two distinct forms: endothelial and metabolic, with the former predominantly affecting vascular endothelial cells and the latter primarily impacting peripheral cells. The understanding of endothelial insulin resistance is crucial in comprehending the pathophysiology of cardiovascular complications in type 2 diabetes. Hence, the objective of this study is to examine the correlations, interplays, and molecular pathways linking endothelial insulin resistance and metabolic insulin resistance, with the aim of offering novel insights and scholarly resources for the prevention and management of diabetic vascular complications.

Structurally Minimalized and Druglike TGase2 Inhibitors Based on 7-Aminoquinoline-5,8-dione Scaffolds for the Treatment of Diabetic Retinopathy

Diabetic retinopathy is a disease that can cause vision loss leading to blindness in people with diabetes. Improved methods to treat and prevent vision loss in diabetic patients are in high demand owing to limited current treatment procedures. Herein, we report a new class of transglutaminase 2 (TGase2) inhibitors for the treatment of diabetic retinopathy based on 7-aminoquinoline-5,8-dione derivatives. 7-Amino-2-phenylquinoline-5,8-dione 11 and 7-amino-2-{4-[(1-methylpiperidin-4-yl)oxy]phenyl}quinoline-5,8-dione 23 exhibited potent inhibitory activities against TGase2 in a fibrinogen array-based on-chip TGase2 activity assay and in an in situ assay in human retinal microvascular endothelial cells, with IC50 values of 5.88 and 1.12 μM in vitro, and 0.09 and 0.07 μM in situ, respectively. Pharmacokinetically favorable 7-amino-2-{4-[(1-isopropylpiperidin-4-yl)oxy] phenyl}quinoline-5,8-dione 22 inhibited vascular leakage in the retinas of streptozotocin-induced diabetic mice via oral administration. Results from the AL5 kinetic assay and a molecular docking study suggest that the inhibitors may bind to TGase2 remote from the active site.

Regulation of AMPK and GAPDH by Transglutaminase 2 Plays a Pivotal Role in Microvascular Leakage in Diabetic Retinas

Diabetic retinopathy is the most common microvascular complication caused by chronic hyperglycemia and is a leading cause of blindness; however, the underlying molecular mechanism has not been clearly elucidated. Therefore, we investigated whether regulation of AMPK and GAPDH by transglutaminase 2 (TGase2) is important for hyperglycemia-induced microvascular leakage in the diabetic retina. In human retinal endothelial cells (HRECs) and diabetic mouse retinas, we found that TGase2, activated by sequential elevation of intracellular Ca2+ and reactive oxygen species (ROS) levels, played an essential role in hyperglycemia-induced vascular leakage. ROS generation and TGsae2 activation were involved in hyperglycemia-induced AMPK dephosphorylation, which resulted in vascular endothelial-cadherin (VE-cadherin) disassembly and increased fluorescein isothiocyanate-dextran extravasation. Furthermore, high glucose-induced TGase2 activation suppressed GAPDH activity, determined by an on-chip activity assay, through inhibition of AMPK, which induced VE-cadherin disassembly and endothelial permeability in HRECs. Overall, our findings suggest that inhibition of AMPK and GAPDH by TGase2 plays a pivotal role in hyperglycemia-induced microvascular leakage in the retinas of diabetic mice.

ARTICLE HIGHLIGHTS

Transglutaminase 2 in diabetes mellitus: Unraveling its multifaceted role and therapeutic implications for vascular complications

Diabetes, a severe metabolic disease characterized by chronic hypoglycemia, poses debilitating and life-threatening risks of microvascular and macrovascular complications, including blindness, kidney failure, heart attacks, and limb amputation. Addressing these complications is paramount, urging the development of interventions targeting diabetes-associated vascular dysfunctions. To effectively combat diabetes, a comprehensive understanding of the pathological mechanisms underlying complications and identification of precise therapeutic targets are imperative. Transglutaminase 2 (TGase2) is a multifunctional enzyme implicated in the pathogenesis of diverse diseases such as neurodegenerative disorders, fibrosis, and inflammatory conditions. TGase2 has recently emerged as a key player in both the pathogenesis and therapeutic intervention of diabetic complications. This review highlights TGase2 as a therapeutic target for diabetic complications and explores TGase2 inhibition as a promising therapeutic approach in their treatment.

The correlation between admission hyperglycemia and 30-day readmission after hip fracture surgery in geriatric patients: a propensity score-matched study

Purpose

This study aimed to investigate the association between admission hyperglycemia and 30-day readmission after hip fracture surgery in geriatric patients.

Methods

This retrospective study included 1253 geriatric hip fracture patients. Patients were categorized into normoglycemia(<6.10 mmol/L) and hyperglycemia groups(≥6.10 mmol/L) based on admission blood glucose. We performed multivariable logistic regression analyses and propensity score matching (PSM) to estimate adjusted odds ratios and 95% confidence intervals for 30-day readmission, controlling for potential confounding factors. An analysis of the dose-dependent association between admission blood glucose and the probability of 30-day readmission was performed. Additional subgroup analysis was conducted to examine the impact of other factors on the relationship between admission blood glucose and 30-day readmission.

Results

Patients with hyperglycemia had higher 30-day readmission rates than normoglycemic patients before (19.1% vs 9.7%, p<0.001) and after PSM (18.1% vs 12.3%, p=0.035). Admission hyperglycemia was an independent predictor of increased 30-day readmission risk, with an adjusted odds ratio of 1.57 (95% CI 1.08-2.29, p=0.019) after multivariable regression and 1.57 (95% CI 1.03-2.39, p=0.036) after PSM. A dose-response relationship was observed between higher glucose levels and increased readmission risk.

Conclusion

Admission hyperglycemia is an independent risk factor for 30-day readmission after hip fracture surgery in the elderly. Routine glucose testing upon admission and perioperative glycemic control may help reduce short-term readmissions in this vulnerable population.

ADAMTS13 inhibits H2O2-induced human venous endothelial cell injury to attenuate deep-vein thrombosis by blocking the p38/ERK signaling pathway

Deep vein thrombosis (DVT) is a common complication in hematologic malignancies and immunologic disorders. Endothelial cell injury and dysfunction comprise the critical contributor for the development of DVT. A disintegrin and metalloproteinase with thrombospondin motifs 13 (ADAMTS13), a plasma metalloprotease that cleaves von Willebrand factor, acts as a critical regulator in normal hemostasis. This study was aimed to explore the role of ADAMTS13 in endothelial cell injury during DVT and the possible mechanism. First, human umbilical vein endothelial cells (HUVECs) were exposed to hydrogen peroxide (H2O2). Then, the mRNA and protein expressions of ADAMTS13 were evaluated with the reverse transcription-quantitative polymerase chain reaction and western blot. After treatment with recombinant ADAMTS13 (rADAMTS13; rA13), the viability and apoptosis of H2O2-induced HUVECs were assessed by cell counting kit-8 assay and terminal-deoxynucleoitidyl transferase-mediated nick end labeling staining. In addition, the levels of prostaglandin F1-alpha, endothelin-1, and reactive oxygen species were detected using the enzyme-linked immunosorbent assay and dichloro-dihydro-fluorescein diacetate assay. The expressions of proteins related to p38/extracellular signal-regulated kinase (ERK) signaling pathway were estimated with the western blot. Then, p79350 (p38 agonist) was used to pretreat cells to analyze the regulatory effects of rA13 on p38/ERK signaling in H2O2-induced HUVEC injury. The results revealed that ADAMTS13 expression was significantly downregulated in H2O2-induced HUVECs. The reduced viability and increased apoptosis of HUVECs induced by H2O2 were revived by ADAMTS13. ADAMTS13 also suppressed the oxidative stress in HUVECs after H2O2 treatment. Besides, ADAMTS13 was found to block p38/ERK signaling pathway, and p79350 reversed the impacts of ADAMTS13 on the damage of HUVECs induced by H2O2. To sum up, ADAMTS13 could alleviate H2O2-induced HUVEC injury through the inhibition of p38/ERK signaling pathway.

Therapeutic effect of ultra-long-lasting human C-peptide delivery against hyperglycemia-induced neovascularization in diabetic retinopathy

Rationale: Neovascularization is a hallmark of the late stages of diabetic retinopathy (DR) leading to blindness. The current anti-DR drugs have clinical disadvantages including short circulation half-lives and the need for frequent intraocular administration. New therapies with long-lasting drug release and minimal side effects are therefore needed. We explored a novel function and mechanism of a proinsulin C-peptide molecule with ultra-long-lasting delivery characteristics for the prevention of retinal neovascularization in proliferative diabetic retinopathy (PDR). Methods: We developed a strategy for ultra-long intraocular delivery of human C-peptide using an intravitreal depot of K9-C-peptide, a human C-peptide conjugated to a thermosensitive biopolymer, and investigated its inhibitory effect on hyperglycemia-induced retinal neovascularization using human retinal endothelial cells (HRECs) and PDR mice. Results: In HRECs, high glucose conditions induced oxidative stress and microvascular permeability, and K9-C-peptide suppressed those effects similarly to unconjugated human C-peptide. A single intravitreal injection of K9-C-peptide in mice resulted in the slow release of human C-peptide that maintained physiological levels of C-peptide in the intraocular space for at least 56 days without inducing retinal cytotoxicity. In PDR mice, intraocular K9-C-peptide attenuated diabetic retinal neovascularization by normalizing hyperglycemia-induced oxidative stress, vascular leakage, and inflammation and restoring blood-retinal barrier function and the balance between pro- and anti-angiogenic factors. Conclusions: K9-C-peptide provides ultra-long-lasting intraocular delivery of human C-peptide as an anti-angiogenic agent to attenuate retinal neovascularization in PDR.

Simultaneous attenuation of hyperglycemic memory-induced retinal, pulmonary, and glomerular dysfunctions by proinsulin C-peptide in diabetes

BACKGROUND

Hyperglycemic memory (HGM) is a pivotal phenomenon in the development of diabetic complications. Although coincident diabetic complications are reported, research on their development and treatment is limited. Thus, we investigated whether C-peptide can simultaneously inhibit HGM-induced retinal, pulmonary, and glomerular dysfunctions in diabetic mice supplemented with insulin.

METHODS

Insulin-treated diabetic mice were supplemented with human C-peptide by subcutaneous implantation of K9-C-peptide depots for 4 weeks, and reactive oxygen species (ROS) generation, transglutaminase (TGase) activity, and vascular leakage were examined in the retina, lung, and kidney.

RESULTS

We found hyperglycemia-induced persistent ROS generation and TGase activation after blood glucose normalization in the retina, lung, and kidney of insulin-supplemented diabetic mice. These pathological events were inhibited by systemic supplementation of human C-peptide via subcutaneous implantation of a thermosensitive biopolymer-conjugated C-peptide depot. ROS generation and TGase activation were in a vicious cycle after glucose normalization, and C-peptide suppressed the vicious cycle and subsequent endothelial permeability in human retinal endothelial cells. Moreover, C-peptide supplementation ameliorated HGM-induced retinal vascular leakage and neurodegeneration, pulmonary vascular leakage and fibrosis, and glomerular adherens junction disruption and vascular leakage.

CONCLUSIONS

Overall, our findings demonstrate that C-peptide supplementation simultaneously attenuates vascular and neuronal dysfunctions in the retina, lung, and glomerulus of insulin-supplemented diabetic mice.

Systemic C-peptide supplementation ameliorates retinal neurodegeneration by inhibiting VEGF-induced pathological events in diabetes

Diabetic retinopathy (DR) is caused by retinal vascular dysfunction and neurodegeneration. Intraocular delivery of C-peptide has been shown to be beneficial against hyperglycemia-induced microvascular leakage in the retina of diabetes; however, the effect of C-peptide on diabetes-induced retinal neurodegeneration remains unknown. Moreover, extraocular C-peptide replacement therapy against DR to avoid various adverse effects caused by intravitreal injections has not been studied. Here, we demonstrate that systemic C-peptide supplementation using osmotic pumps or biopolymer-conjugated C-peptide hydrogels ameliorates neurodegeneration by inhibiting vascular endothelial growth factor-induced pathological events, but not hyperglycemia-induced vascular endothelial growth factor expression, in the retinas of diabetic mice. C-peptide inhibited hyperglycemia-induced activation of macroglial and microglial cells, downregulation of glutamate aspartate transporter 1 expression, neuronal apoptosis, and histopathological changes by a mechanism involving reactive oxygen species generation in the retinas of diabetic mice, but transglutaminase 2, which is involved in retinal vascular leakage, is not associated with these pathological events. Overall, our findings suggest that systemic C-peptide supplementation alleviates hyperglycemia-induced retinal neurodegeneration by inhibiting a pathological mechanism, involving reactive oxygen species, but not transglutaminase 2, in diabetes.

Dopamine ameliorates hyperglycemic memory-induced microvascular dysfunction in diabetic retinopathy

Dopamine is a neurotransmitter that mediates visual function in the retina and diabetic retinopathy (DR) is the most common microvascular complication of diabetes and the leading cause of blindness; however, the role of dopamine in retinal vascular dysfunction in DR remains unclear. Here, we report a mechanism of hyperglycemic memory (HGM)-induced retinal microvascular dysfunction and the protective effect of dopamine against the HGM-induced retinal microvascular leakage and abnormalities. We found that HGM induced persistent oxidative stress, mitochondrial membrane potential collapse and fission, and adherens junction disassembly and subsequent vascular leakage after blood glucose normalization in the mouse retinas. These persistent hyperglycemic stresses were inhibited by dopamine treatment in human retinal endothelial cells and by intravitreal injection of levodopa in the retinas of HGM mice. Moreover, levodopa supplementation ameliorated HGM-induced pericyte degeneration, acellular capillary and pericyte ghost generation, and endothelial apoptosis in the mouse retinas. Our findings suggest that dopamine alleviates HGM-induced retinal microvascular leakage and abnormalities by inhibiting persistent oxidative stress and mitochondrial dysfunction.

KDM3A Inhibition Ameliorates Hyperglycemia-Mediated Myocardial Injury by Epigenetic Modulation of Nuclear Factor Kappa-B/P65

Objectives

Even after the glucose level returns to normal, hyperglycemia-induced cardiac dysfunction as well as reactive oxygen species (ROS) generation, inflammatory responses, and apoptosis continued deterioration, showing a long-lasting adverse effect on cardiac function and structure. We aimed to unveil the molecular and cellular mechanisms underlying hyperglycemia-induced persistent myocardial injury and cardiac dysfunction.

Methods and Results

Recently, the accumulated evidence indicated epigenetic regulation act as a determining factor in hyperglycemia-induced continuous cardiovascular dysfunction. As an important histone demethylase, the expression of lysine-specific demethylase 3A (KDM3A) was continually increased, accompanied by a sustained decline of H3K9me2 levels in diabetic myocardium even if received hypoglycemic therapy. Besides, by utilizing gain- and loss-of-functional approaches, we identified KDM3A as a novel regulator that accelerates hyperglycemia-mediated myocardial injury by promoting ROS generation, aggregating inflammatory reaction, and facilitating cell apoptosis in vitro and in vivo. The KDM3A inhibition could significantly ameliorate the adverse effect of hyperglycemia in both diabetes model and diabetic intensive glycemic control model. Mechanically, our data uncovered that KDM3A could promote the expression and transcriptional activity of nuclear factor kappa-B (NF-κB/P65), and the succedent rescue experiments further verified that KDM3A regulates hyperglycemia-induced myocardial injury in an NF-κB/P65 dependent manner.

Conclusion

This study revealed histone-modifying enzymes KDM3A drives persistent oxidative stress, inflammation, apoptosis, and subsequent myocardial injury in the diabetic heart by regulating the transcription of NF-κB/P65.

Midazolam Ameliorates Hyperglycemia-Induced Glomerular Endothelial Dysfunction by Inhibiting Transglutaminase 2 in Diabetes

Midazolam is an anesthetic widely used for anxiolysis and sedation; however, to date, a possible role for midazolam in diabetic kidney disease remains unknown. Here, we investigated the effect of midazolam on hyperglycemia-induced glomerular endothelial dysfunction and elucidated its mechanism of action in kidneys of diabetic mice and human glomerular microvascular endothelial cells (HGECs). We found that, in diabetic mice, subcutaneous midazolam treatment for 6 weeks attenuated hyperglycemia-induced elevation in urine albumin/creatinine ratios. It also ameliorated hyperglycemia-induced adherens junction disruption and subsequent microvascular leakage in glomeruli of diabetic mice. In HGECs, midazolam suppressed high glucose-induced vascular endothelial-cadherin disruption and endothelial cell permeability via inhibition of intracellular Ca²⁺ elevation and subsequent generation of reactive oxygen species (ROS) and transglutaminase 2 (TGase2) activation. Notably, midazolam also suppressed hyperglycemia-induced ROS generation and TGase2 activation in glomeruli of diabetic mice and markedly improved pathological alterations in glomerular ultrastructure in these animals. Analysis of kidneys from diabetic Tgm2^−/− mice further revealed that TGase2 played a critical role in microvascular leakage. Overall, our findings indicate that midazolam ameliorates hyperglycemia-induced glomerular endothelial dysfunction by inhibiting ROS-mediated activation of TGase2.

Hyperglycemic memory in diabetic cardiomyopathy

Cardiovascular diseases account for approximately 80% of deaths among individuals with diabetes mellitus, with diabetic cardiomyopathy as the major diabetic cardiovascular complication. Hyperglycemia is a symptom that abnormally activates multiple downstream pathways and contributes to cardiac hypertrophy, fibrosis, apoptosis, and other pathophysiological changes. Although glycemic control has long been at the center of diabetes therapy, multicenter randomized clinical studies have revealed that intensive glycemic control fails to reduce heart failure-associated hospitalization and mortality in patients with diabetes. This finding indicates that hyperglycemic stress persists in the cardiovascular system of patients with diabetes even if blood glucose level is tightly controlled to the normal level. This process is now referred to as hyperglycemic memory (HGM) phenomenon. We briefly reviewed herein the current advances that have been achieved in research on the underlying mechanisms of HGM in diabetic cardiomyopathy.

Alterations of transcriptome expression, cell cycle, and mitochondrial superoxide reveal foetal endothelial dysfunction in Saudi women with gestational diabetes mellitus

Gestational diabetes mellitus (GDM) affects one in four Saudi women and is associated with high risks of cardiovascular diseases in both the mother and foetus. It is believed that endothelial cells (ECs) dysfunction initiates these diabetic complications. In this study, differences in the transcriptome profiles, cell cycle distribution, and mitochondrial superoxide (MTS) between human umbilical vein endothelial cells (HUVECs) from GDM patients and those from healthy (control) subjects were analysed. Transcriptome profiles were generated using high-density expression microarray. The selected four altered genes were validated using qRT-PCR. MTS and cell cycle were analysed by flow cytometry. A total of 84 altered genes were identified, comprising 52 upregulated and 32 downregulated genes in GDM.HUVECs. Our selection of the four interested altered genes (TGFB2, KITLG, NEK7, and IGFBP5) was based on the functional network analysis, which revealed that these altered genes are belonging to the highest enrichment score associated with cellular function and proliferation; all of which may contribute to ECs dysfunction. The cell cycle revealed an increased percentage of cells in the G2/M phase in GDM.HUVECs, indicating cell cycle arrest. In addition, we found that GDM.HUVECs had increased MTS generation. In conclusion, GDM induces persistent impairment of the biological functions of foetal ECs, as evidenced by analyses of transcriptome profiles, cell cycle, and MTS even after ECs culture in vitro for several passages under normal glucose conditions.

Apelin/APJ relieve diabetic cardiomyopathy by reducing microvascular dysfunction

Microcirculatory injuries had been reported to be involved in diabetic cardiomyopathy, which was mainly related to endothelial cell dysfunction. Apelin, an adipokine that is upregulated in diabetes mellitus, was reported to improve endothelial cell dysfunction and attenuate cardiac insufficiency induced by ischemia and reperfusion. Therefore, it is hypothesized that apelin might be involved in alleviating endothelial cell dysfunction and followed cardiomyopathy in diabetes mellitus. The results showed that apelin improved endothelial cell dysfunction via decreasing apoptosis and expression of adhesion molecules and increasing proliferation, angiogenesis, and expression of E-cadherin, VEGFR 2 and Tie-2 in endothelial cells, which resulted in the attenuation of the capillary permeability in cardiac tissues and following diabetic cardiomyopathy. Meanwhile, the results from endothelial cell-specific APJ knockout mice and cultured endothelial cells confirmed that the effects of apelin on endothelial cells were dependent on APJ and the downstream NFκB pathways. In conclusion, apelin might reduce microvascular dysfunction induced by diabetes mellitus via improving endothelial dysfunction dependent on APJ activated NFκB pathways.

Application of elastin-like biopolymer-conjugated C-peptide hydrogel for systemic long-term delivery against diabetic aortic dysfunction

Due to their short half-lives, repeated administration of anti-hyperglycemic drugs can cause pain, discomfort, tissue damage, and infection in diabetic patients. Therefore, there is a need to develop long-term drug delivery systems to treat diabetes and its complications. C-peptide can prevent diabetic complications, including diabetic vasculopathy, but its clinical application is limited by its short half-life. Here, we developed K9-C-peptide (human C-peptide conjugated to an elastin-like biopolymer) and investigated its long-term influence on hyperglycemia-induced vascular dysfunction using an aortic endothelium model in diabetic mice. Using pharmacokinetics and in vivo imaging, we found that subcutaneously injected K9-C-peptide formed a hydrogel depot that slowly released human C-peptide into the blood circulation for 19 days. Administration of K9-C-peptide, human C-peptide, or K8 polypeptide had no effect on body weight or blood glucose levels. The slow release of C-peptide from K9-C-peptide hydrogels provided prolonged prevention of oxidative stress, inflammatory responses, and endothelial apoptosis in a hyperglycemia-induced vascular dysfunction model using the diabetic mouse aorta. Subcutaneous administration of unbound human C-peptide and K8 polypeptide were used as negative controls and had no effects. These results suggest that K9-C-peptide is suitable for the long-term delivery of human C-peptide for treating vascular dysfunction in diabetic patients.

Transglutaminase 2 Inhibitor LDN 27219 Age-Dependently Lowers Blood Pressure and Improves Endothelium-Dependent Vasodilation in Resistance Arteries

Transglutaminase 2 (TG2) is an enzyme which in the open conformation exerts transamidase activity, leading to protein cross-linking and fibrosis. In the closed conformation, TG2 participates in transmembrane signaling as a G protein. The unspecific transglutaminase inhibitor cystamine causes vasorelaxation in rat resistance arteries. However, the role of TG2 conformation in vascular function is unknown. We investigated the vascular effects of selective TG2 inhibitors by myography in isolated rat mesenteric and human subcutaneous resistance arteries, patch-clamp studies on vascular smooth muscle cells, and blood pressure measurements in rats and mice. LDN 27219 promoted the closed TG2 conformation and inhibited transamidase activity in mesenteric arteries. In contrast to TG2 inhibitors promoting the open conformation (Z-DON, VA5), LDN 27219 concentration-dependently relaxed rat and resistance human arteries by a mechanism dependent on nitric oxide, large-conductance calcium-activated and voltage-gated potassium channels 7, lowering blood pressure. LDN 27219 also potentiated acetylcholine-induced relaxation by opening potassium channels in the smooth muscle; these effects were abolished by membrane-permeable TG2 inhibitors promoting the open conformation. In isolated arteries from 35- to 40-week-old rats, transamidase activity was increased, and LDN 27219 improved acetylcholine-induced relaxation more than in younger rats. Infusion of LDN 27219 decreased blood pressure more effectively in 35- to 40-week than 12- to 14-week-old anesthetized rats. In summary, pharmacological modulation of TG2 to the closed conformation age-dependently lowers blood pressure and, by opening potassium channels, potentiates endothelium-dependent vasorelaxation. Our findings suggest that promoting the closed conformation of TG2 is a potential strategy to treat age-related vascular dysfunction and lowers blood pressure.

Neuronal and Endothelial Transglutaminase-2 Expression during Experimental Autoimmune Encephalomyelitis and Multiple Sclerosis

Transglutiminase-2 (TG2) is a multifunctional enzyme that has been implicated in the pathogenesis of experimental autoimmune encephalomyelitis (EAE) and multiple sclerosis (MS) using global knockout mice and TG2 selective inhibitors. Previous studies have identified the expression of TG2 in subsets of macrophages-microglia and astrocytes after EAE. The aims of the current investigation were to examine neuronal expression of TG2 in rodent models of chronic-relapsing and non-relapsing EAE and through co-staining with intracellular and cell death markers, provide insight into the putative role of TG2 in neuronal pathology during disease progression. Here we report that under normal physiological conditions there is a low basal expression of TG2 in the nucleus of neurons, however following EAE or MS, robust induction of cytoplasmic TG2 occurs in most neurons surrounding perivascular lesion sites. Importantly, TG2-positive neurons also labeled for phosphorylated Extracellular signal-regulated kinase 1/2 (ERK1/2) and the apoptotic marker cleaved caspase-3. In white and gray matter lesions, high levels of TG2 were also found within the vasculature and endothelial cells as well as in tissue migrating pericytes or fibroblasts, though rarely did TG2 colocalize with cells identified with glial cell markers (astrocytes, oligodendrocytes and microglia). TG2 induction occurred concurrently with the upregulation of the blood vessel permeability factor and angiogenic molecule Vascular Endothelial Growth Factor (VEGF). Extracellular TG2 was found to juxtapose with fibronectin, within and surrounding blood vessels. Though molecular and pharmacological studies have implicated TG2 in the induction and severity of EAE, the cell autonomous functions of this multifunctional enzyme during disease progression remains to be elucidated.

Overexpression of MicroRNA-122 Resists Oxidative Stress-Induced Human Umbilical Vascular Endothelial Cell Injury by Inhibition of p53

Deep venous thrombosis (DVT) constitutes a great threat to health worldwide. Endothelial cell injury and dysfunction comprise the critical contributor for the development of DVT. However, the mechanism behind it remains poorly elucidated. The study is aimed at investigating the role of microRNA-122 (miR-122) and oxidative stress on DVT. The results showed that miR-122 overexpression dampened H₂O₂-evoked cytotoxic injury in human umbilical vein endothelial cells (HUVECs) by increasing cell viability, suppressing cell apoptosis and oxidative stress injury. Notably, miR-122 overexpression attenuated provasoconstriction factor endothelin-1 (ET-1) expression in HUVECs exposed to H₂O₂ but enhanced the productions of vasodilatation factor Prostaglandin F1α (PGF1α). Moreover, inhibition of miR-122 had the opposite results. miR-122 could inhibit the expression of p53. Low expression of p53 could enhance the protection of miR-122 on HUVEC injury. This study highlights that miR-122 overexpression may restore H₂O₂-induced HUVEC injury by regulating the expression of p53.

Increased Transglutaminase 2 Expression and Activity in Rodent Models of Obesity/Metabolic Syndrome and Aging

Diastolic dysfunction of the heart and decreased compliance of the vasculature and lungs (i.e., increased organ tissue stiffness) are known features of obesity and the metabolic syndrome. Similarly, cardiac diastolic dysfunction is associated with aging. Elevation of the enzyme transglutaminase 2 (TG2) leads to protein cross-linking and enhanced collagen synthesis and participates as a candidate pathway for development of tissue stiffness. With these observations in mind we hypothesized that TG2 may be elevated in tissues of a rat model of obesity/metabolic syndrome (the ZSF 1 rat) and a mouse model of aging, i.e., the senescent SAMP8 mouse. In the experiments reported here, TG2 expression and activity were found for the first time to be spontaneously elevated in organs from both the ZSF1 rat and the SAMP8 mouse. These observations are consistent with a hypothesis that a TG2-related pathway may participate in the known tissue stiffness associated with cardiac diastolic dysfunction in these two rodent models. The potential TG2 pathway needs better correlation with physiologic dysfunction and may eventually provide novel therapeutic insights to improve tissue compliance.

The vicious cycle between ferritinophagy and ROS production triggered EMT inhibition of gastric cancer cells was through p53/AKT/mTor pathway

Cancer metastasis and resistance for chemotherapeutic agent correlate with epithelial-mesenchymal transition (EMT), while ROS production also involves in the EMT process, However, how autophagy mediated ROS production affects EMT remains unclear. Previous study showed that DpdtC (2,2'-di-pyridylketone hydrazone dithiocarbamate) could induce ferritinophagy in HepG2 cell. To insight into more details that how ferritinophagy affects cellular feature, the SGC-7901and BGC-823 gastric cancer cell lines were used. Interestingly DpdtC treatment resulted in EMT inhibition and was ROS dependent. Similar situation occurred in TGF-β1 induced EMT model, supporting that DpdtC was able to inhibit EMT. Next the ability of DpdtC in ferritinophagy induction was further evaluated. As expected, DpdtC induced ferritinophagy in the absence and presence of TGF-β1. The correlation analysis revealed that an enhanced ferritinophagic flux contributed to the EMT inhibition. In addition, ferritinophagy triggers Fenton reaction, resulting in ROS production which give rise of p53 response, thus the role of p53 was further investigated. DpdtC treatment resulted in upregulation of p53, but, the addition of p53 inhibitor, PFT-α could significantly neutralize the action of DpdtC on ferritinophagy induction and EMT inhibition. Furthermore, autophagy inhibitors or NAC could counteract the action of DpdtC, indicating that ferrtinophagy-mediated ROS played an important role in the cellular events. In addition to upregulation of p53, its down-stream targets, AKT/mTor were also downregulated, supporting that DpdtC induced EMT inhibition was achieved through ferritinophagy-ROS vicious cycle mediated p53/AKT/mTor pathway. And the activation of ferritinophagic flux was the dominant driving force in action of DpdtC in gastric cancer cells.

Molecular hydrogen improves type 2 diabetes through inhibiting oxidative stress

The aim of the present study was to investigate the potential therapeutic effects of molecular hydrogen on type 2 diabetes mellitus (T2DM) in rats. Following maintenance on a high-fat diet for 4 weeks, a T2DM model was established using an injection of 30 mg/kg streptozotocin via the caudal vein into Sprague-Dawley rats. On day 0 and Day 80, the blood samples were obtained from each rat for the measurement of biochemical indicators including blood lipids, fasting blood glucose, hepatic glycogen, fasting serum insulin, insulin sensitivity index, insulin resistance index, serum superoxide dismutase (SOD) and serum malondialdehyde (MDA) using an automatic biochemical analyzer. The kidneys and pancreas tissues were harvested for HE staining and Western blot assay of toll-like receptor 4 (TLR4), myeloid differentiation primary response 88 (MyD88), phosphorylated (p)-p65, p65, p-IκB and IκB. The results showed that in rats with T2DM, molecular hydrogen treatment decreased fasting blood glucose levels, increased hepatic glycogen synthesis and improved insulin sensitivity. Treatment with molecular hydrogen also increased the production of SOD whilst decreasing the production of MDA. In addition, molecular hydrogen alleviated the pathological changes exhibited by pancreatic islets and kidney during T2DM. Mechanistically, molecular hydrogen decreased TLR4 and MyD88 expression levels whilst also decreasing p65 and NF-κB inhibitor phosphorylation. In conclusion, molecular hydrogen exerted therapeutic effects against T2DM by improving hyperglycemia and inhibiting oxidative stress through mechanisms that are associated with the TLR4/MyD88/NF-κB signaling pathway.

Anti-metastatic effect of midazolam on melanoma B16F10 cells in the lungs of diabetic mice

Midazolam is an anesthetic agent commonly used for anesthesia and sedation in surgery. However, there is no information on the role of midazolam in hyperglycemia-induced cancer metastasis to date. In this study, we investigated the effects of midazolam on inhibiting metastases in the lungs of diabetic mice and on human pulmonary microvascular endothelial cells (HPMVECs). Subcutaneous injection of midazolam inhibited hyperglycemia-induced cancer metastasis in the lungs of diabetic mice. Midazolam also prevented the generation of ROS, activation of TGase, and subsequent vascular leakage in the lungs of diabetic mice. Furthermore, in vitro studies with HPMVECs confirmed that midazolam inhibited VEGF-induced intracellular events including ROS generation, TGase activation, and disruption of vascular endothelial-cadherins, thus preventing the permeability of endothelial cells. Notably, midazolam had no direct effect on the migration or proliferation of melanoma cells, instead acting upon endothelial cells. The midazolam-mediated inhibition of VEGF-induced intracellular events was reversed by treatment with the GABA_A receptor antagonist flumazenil. These findings suggest that midazolam prevents hyperglycemia-induced cancer metastasis by inhibiting VEGF-induced intracellular events and subsequent vascular leakage via the GABA_A receptors in the lungs of diabetic mice.